These stats are experimental and while we usually get very accurate numbers we can't guarantee they are 100% spot on.
You can however view the endroundstats: Those are the endroundstats 1:1 how they were spammed on the server console, they are guaranteed to be correct (unless they're off, which sometimes happens too :p).
Some examples that will definitely break stats:

Server crash / restart

Players reconnecting with new ids

Too many random renames between rounds

Credits to the author of StatWhore
of which we borrowed the awards and the general layout of the stats.Thanks toHannes who made the software that extracts all the stats from tv demos available to us.